1. Field of the Invention
This invention relates to a catheter introducing instrument well-suited for introducing a catheter into a blood vessel.
2. Description of the Prior Art
In order to introduce a catheter into a blood vessel through the skin, the practice in the prior art is to use an introducing needle, a guide wire and a dilator. More specifically, the introducing needle, which comprises an inner needle portion and a cover tube, is used to pierce the desired blood vessel, after which only the inner needle portion is withdrawn. The guide wire is then inserted into the blood vessel by being passed through the cover tube, which has been left in place. This is followed by withdrawing the cover tube, leaving the guide wire in place. Next, the dilator is so inserted as to fit over the guide wire and functions to dilate the opening made in the subcutaneous tissue and in the wall of the blood vessel, thus making it possible to reduce resistance which the catheter meets in being inserted through the subcutaneous tissue and blood vessel wall. This is followed by withdrawing the dilator from the guide wire and fitting the catheter over the guide wire so that the catheter may then be introduced into the blood vessel.
The conventional method described above is disadvantageous in that the preparation and handling of the instruments is of some complexity, it being necessary to furnish the introducing needle, which makes it possible to insert the guide wire into the blood vessel so that the catheter can be introduced into the blood vessel through the skin, as well as the dilator for spreading the subcutaneous tissue and the opening in the blood vessel wall to facilitate the introduction of the catheter. Furthermore, since it is necessary to insert the guide wire into the blood vessel from the cover tube of the introducing needle, withdraw the cover tube and then insert the dilator into the blood vessel by fitting the dilator over the guide wire, it is required that the patient be punctured twice. This not only involves a complicated operating procedure but also subjects the patient to a considerable burden.